Transfer medium for typing on non-receptive surfaces



United States Patent 3,387,986 TRANSFER MEDIUM FOR TYPING 0N NflN-REQEPTIVE SURFACES Donald L. Elbert and William H. Horne, Lexington, Ky.,

assignors to international Business Machines Corporation, Arrnonk, N.Y., a corporation of New York No Drawing. Filed Apr. 1, 1965, Ser. No. 444,810 Claims. (Cl. 117-361) ABSTRACT 0F THE DISCLOSURE A transfer medium is suitable for typing on smooth surfaces which have substantially no minute voids or openings, such as translucent or transparent plastics. The transfer medium includes a substrate coated with a transfer layer which layer is pressure sensitive and comprises a major portion of a pigment material, such as carbon black and minor proportions of wax and resin which resin is a pressure sensitive adhesive, such as solid, normally tacky silicone resins. The pressure sensitive adhesive causes the material to firmly adhere to the smooth surface upon transfer by a type die.

This invention relates to the art of transfer mediums, particularly typewriter ribbons. More particularly, the invention provides a transfer medium for typing on nonreceptive surfaces such as transparent plastic surfaces.

The need for a transfer medium suitable for typing on non-receptive surfaces has been recognized in the prior art. Generally, of course, it is desired to type on ordinary paper. The significant porosity of paper is utilized in the prior art to absorb a fluid or pasty transfer medium. Drying of transfer medium on paper may, in some cases, result from a mere spreading and holding of the transfer medium by capillary action. For other transfer mediums, particularly of the pasty sort found on conventional carbon papers, the action may not be a drying at all, but rather a mechanical bond between the waxes of the transfer medium and the fibers of the paper. In summary, it can be said that the permanent setting of a transfer medium on a porous or fibrous base, such as paper, is not a significant problem in the art.

This invention is concerned in particular with typing on relatively smooth substrates having substantially no minute voids or openings. Such substrates are generally a translucent or transparent plastic such as polyethylene glycol terephthalate, and it is the translucency or transparency of the substrate which is generally the beneficial property in its use. The typed figures on the transparent substrate can be used as desired in optical systems. Transparent substrates carrying typed intelligence may be used in the television broadcasting industry along with magnifying and projecting optics to display a text on a screen for reading by television commentators and performers. Another utilization definitely contemplated is the typing of lettering on inexpensive translucent sheets which will also carry figures drawn by conventional drafting techniques. Copies would be made as required with the use of conventional copying techniques. Purely as an example, transparent or translucent substrates carrying typed intelligence could be used as a part of an information storage system in which the substrates are processed through the powerful ultraviolet optics now generally required to produce inexpensive, diazoniurn copies.

Prior art transfer mediums to type on non-porous and otherwise nonreceptive substrates are unsatisfactory. The general approach has been to provide a solvated vehicle as a transfer layer in which the solvent leaves the layer after transfer to the substrate. The theory is that a dry colored residue will permanently remain on the substrate. This prior art has not one salient disadvantage, but many:

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( 1) the solvent must be volatile, thus inherently creating a problem of the transfer medium drying and becoming inoperative before use; (2) a transferred image carries solvent for a substantial, finite time during which the image must be protected against smearing; (3) in order to achieve balance between ribbon life due to non-drying of the solvent and reasonably quick use of the printed image, differences between the environment of the ribbon and the environment of the printed image are dictated. This implies the need for a drying oven for the printed image; an expensive, unwieldy, and potentially troublesome addition to the typing system; and (4) a delicate chemical balance must be maintained in the transfer medium to prevent the dried residue from appearing as grains. Grains would rub easily from the substrate. The binding materials and the coloring matter used are therefore limited to the point that a good, commercially acceptable print is probably unattainable with the use of the prior art. In fact many of the imaging materials used in the prior art tend to decompose under the influence of light or other actinic radiation. At least one prior art teaching includes the use of a solvent which is a partial solvent for the substrate. The problem of graining would persist, however, with only the base layer being strongly held by interlocking molecules resulting from the drying of the solvent.

The object of this invention is to create a practical and economic transfer medium for use with non-receptive surfaces.

This invention differs from the prior art by its use of a dry transfer medium designed after careful study of the system in which it will be used. The use of a dry transfer medium initially creates problems having to do with complete and permanent transfer during printing. These problems have been solved, however, in accordance with this invention. The resulting product has long life under extreme environmental factors, the product is operative with conventional typewriters without the addition of a single accessory for use with the product, the product may be formulated carrying imaging material of virtually any shade, color, and texture; and the product provides an instantaneous, finished write which has good image definition and quality. The product is also economically attractive in regard to cost of fabrication, cost of materials, and cost of handling.

In accordance with the invention a transfer layer is compounded which consists of a colored material of significant internal strength which is pressure sensitive and responds to significant pressures to become tacky in the manner of a pressure sensitive adhesive. Preferably, the coloring is supplied by conventional imaging materials such as carbon black while the pressure sensitive properties are supplied by a material which answers these properties and will carry and be largely colored by the conventional imaging materials. Large amounts of carbon black can be incorporated in the transfer layer in accordance with the preferred aspects of this invention to thereby achieve excellent write quality.

Under the influence of the heavy impact of a type die, an area of the transfer medium corresponding to the character on the type die is moved and formed into intimate and substantially complete contact with the receiving substrate. When the type die is removed the stresses in the entire transfer medium relax, and there is a pull back to the original position. The character areas impressed by the type die are believed to be in smooth and continuous contact with the receiving substrate. The sticking effect realized in accordance with this invention is believed to be entirely comparable to that of a pressure sensitive adhesive. Only the salient features of the type die are transferred to the receiving substrate; transfer layer material in the center of characters returns with the transfer medium as the transfer medium moves to its normal position.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention.

The preferred embodiment of this invention is a typewriter ribbon for use in typing upon any one of several transparent plastic materials, Light-fast carbon black is used as the imaging material in preference to less stable dyes. The product is dry and not tacky or sticky under normal handling and use conditions. The preferred substrate of the typewriter ribbon is a low cost, polyethylene film which is smooth, continuous, and nonporous.

The product is fabricated by solvent coating techniques. Bulk quantities of a solvated and dispersed mixture of the transfer layer are directly applied to bulk quantities of 00005-00006 inch thick polyethylene film in quantitles such that the thickness of the final transfer layer is a preselected thickness which preferably may be within the limits of 0.00025 to 0.00050 inch thick.

The transfer layer mixture is as follows:

Material: Parts/weight (dry) Channel black with dye ppt. (DS 1686-product of Dye Specialties Inc.) 80

Ouriscury wax 10 Normally tacky silicone resin (SR 52lproduct of General Electric Co.) 5

(SR 582-product of General Electric Co.) 5

In the above formula the channel black, in addition to its excellent imaging properties, reduces the internal strength of the transfer layer to thereby allow fracture and transfer. As is well known, channel black is a finely divided, deep black solid. The dye precipitate modifies the color and color tone of the carbon black as is well known in the transfer medium art. The imaging material is at least two-thirds (66 /3 percent) by weight of the transfer layer.

The ouricury wax in the above formula is a component added to prevent flaking and to reduce the internal strength of the transfer layer. Ouricury wax is hard, solid, and dry, but it will fracture upon impact with a type die to permit severing of the solid transfer layer along the edges of a type die. A balance must be obtained in this preferred embodiment to achieve reduction in internal strength of the transfer layer to thereby permit fracture and transfer along the salients of a type die, and yet to provide a transfer medium which does not flake during normal bending and twisting. A blend of 80 percent pigment and 20 percent wax results in a transfer medium which does not flake; however, the transfer medium also does not transfer to non-receptive substrates. On the other hand, a blend of 90 percent pigment and percent silicone transfers satisfactorily, but the flaking during normal handling is at a level generally undesirable and the definition of the printed image is also at a level generally undesirable.

In the preferred formula the wax binds together the entire transfer layer to prevent flaking under normal handling and ribbon feed conditions and the wax also lowers the internal, cohesive strength of the transfer layer to provide better definition of the fracture of the transfer layer along the lines defined by the salients of a type die. Tests indicate that the wax may vary from 2 to 10 parts by weight as against 80 parts carbon black. The characteristics supplied by substantial amounts of the wax negatives the pressure sensitive properties desired for the transfer layer as a whole. Formulations similar to the above, but containing wax at greater than 10 parts, display a reduction in the ability of the transfer layer to be transferred to a plastic substrate material. On the other hand, other hard, waxy substances are considered substantially equivalent to ouricury wax, including but not limited to: phenolic resins, carnauba wax, candellila wax, sugar cane wax.

In the above formula the silicone resins are the basic ingredients which provides the necessary pressure sensitive properties. The two resins used do not differ greatly. Both are used in the preferred formula, but it is believed that the use of 10 parts of either resin would be entirely satisfactory for most applications. Silicon solids tend not to form crystalline structures, as is evidenced particularly by silicon glass. It is this quasi-amorphous nature which appears to be active in this invention. Under the influence of a type die the silicone resin spreads and tightly covers the substrate at areas corresponding to the salient portions of the type die. The silicone tends to wet most substances, and this wetting action further defines a complete, smooth outline of the salient portions of the type die. This area is held in place in the manner of an adhesive while the remaining transfer medium pulls away on the normal return of the typewriter ribbon, Other pressure sensitive materials can function in accordance with this invention. Low molecular weight polyvinyl ethyl ether has been shown to function satisfactorily, although not matching the excellent properties of the silicone resin.

It must be emphasized that an important feature of this invention is in the transfer layer provided being solid and dry. Even though the silicones used are normally tacky when dry, the materials added modify these properties to a level at which the combination is not sticky under normal handling and operating pressures. A typewriter ribbon made in accordance with this invention therefore can be wound in the conventional spool and can be fed by conventional ribbon feed structures. Under the high pressures generated by an impacting type die, the characteristics of a pressure sensitive adhesive appear, and the typed images permanently adhere to normally non-receptive sur faces.

Fabrication of the ribbon is with a solvent coater of the type well known commercially. The machine has an applicator roll which is partly immersed in a pan holding the fluid mixture. The applicator roll carries the fluid mixture up to the substrate. The substrate moves continuously to drying stages. The above mixture is rendered fluid in the following manner:

The channel black with dye precipitate is dispersed with lll-trichloroethane in a ball mill at room temperature. The dispersion is l2 /2% by weight channel black.

The ouricury wax is dissolved in toluene. Heat is applied to facilitate the dissolution of the wax. The solution made is 20% by weight wax.

The SR 521 and the SR 582 are commercially obtained as solutions of 55% resin in toluene. The dry residues are known commercially as pressure sensitive adhesives.

The four components are mixed in proportions dictated by the above formula of solids, accompanied by stirring and heating to F. Grinding or ball milling at this stage is unnecessary.

After fluid coating and evaporation of the fluids, as discussed, the final product appears dry and solid under normal pressures and usual temperatures. The product is typed upon with an ordinary typewriter in the conventional manner. The finished print on a smooth substrate is simultaneous with the moment of impact. Furthermore, a very intense opaque image is obtained because of the high concentration of carbon black in the ink made possible in accordance with this invention.

Although the transfer layer must have significant internal strength so that a permanent image is transferred, it is not meant to imply that the strength must be substantial. Some conventional transfer mediums and typewriter ribbons transfer images to non-receptive substrates. The images transferred, however, are fluid, pasty, or otherwise noncohesive. They can be smeared or wiped off by light contact with environmental objects during normal handling. The significant internal strength provided in accordance with this invention produces an image which holds together in place even though wiped by external objects with pressures normally found in the handling of printed mediums.

This description is not meant to imply that the preferred embodiment herein described functions very well for typing upon every smooth substrate. Excellent results have been achieved in typing upon polyethylene glycol terephthalate, polyethylene, a polyamide, and a rubber hydrochloride. On the other hand, the preferred embodiment provided only fair results when typed upon cellophane. The reasons for this should be clear, however, in view of the teachings of this patent application. The pressure sentitive material must adhere to the substrate typed upon. Transfer layer body materials having significant granular properties are thereby excluded from the beginning. In addition, however, a strong repulsion reaction between the pressure sensitive material and the substrate would negative any adhesive action generally found. One of ordinary skill should be able to practice routine knowledge and experiments to adjust his materials to the characteristics of the substrate to be typed upon.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

We claim:

1. A special purpose transfer medium comprising:

a supporting substrate, and

a transfer layer carried on said substrate, said transfer layer consisting essentially of at least sixty-six and two-thirds percent by weight of finely divided carbon black intimately intermixed with a pressure sensitive mixture of from two to ten percent by weight of a wax component selected from the group consisting of ouricury wax, carnauba wax, candellila wax, and sugar cane wax and at least ten percent by weight of a solid, normally tacky pressure sensitive adhesive selected from the group consisting of silicone resin and low molecular weight polyvinyl ethyl ether to form a solid, dry transfer layer of significant internal strength which becomes tacky under the normal impact of a type die.

2. The article as in claim 1 wherein said finely divided carbon black is channel black.

3. A special purpose transfer medium comprising:

a smooth, continuous, nonporous supporting substrate,

and

a transfer layer carried on said substrate, said transfer layer consisting essentially of at least sixty-six and two-thirds percent by weight of finely divided carbon black intimately intermixed with a pressure sensitive mixture of from two to ten percent by weight of a wax component selected from the group consisting of ouricury wax, carnauba wax, candellila wax, and sugar cane wax and at least ten percent by weight of a solid, normally tacky pressure sensitive adhesive selected from the group consisting of silicone resin and low molecular weight polyvinyl ethyl ether to form a solid, dry transfer layer of significant internal strength which becomes tacky under the normal impact of a type die. 4. The article as in claim 3 wherein said finely divided carbon black is channel black.

5. A special purpose typewriter ribbon comprising: a smooth, continuous, nonporous supporting substrate of polyethylene, and a transfer layer carried on said substrate, said transfer layer being a preselected thickness limited from 0.00025 inch to 0.0005 inch thick, said transfer layer consisting essentially of at least about eighty percent by weight of finely divided carbon black intimately mixed with from two to ten percent by weight of a hard, dry wax filler selected from the group consisting of ouricury wax, carnauba wax, candellila wax, and sugar cane wax and at least ten percent by weight of a solid, normally tacky silicone resin, the combination of which has significant internal strength and becomes tacky under the normal impact of a type die. 6. The article as in claim 5 wherein said carbon black is channel black.

'7. The article as in claim 1 wherein said adhesive is a silicone.

8. The article as in claim 1 wherein said adhesive is a low molecular weight polyvinyl ethyl ether.

9. The article as in claim 3 wherein said adhesive is a silicone.

10. The article as in claim 3 wherein said adhesive i a low molecular weight polyvinyl ethyl ether.

References Cited UNITED STATES PATENTS 2,810,661 10/1957 Newman et al 117-36 1 3,036,924 5/1962 Newman 117-36.1 3,061,454 10/1962 Graf et al l1736.1 3,087,832 4/1963 Fogle ll736.4 3,212,913 10/1965 Mackenzie 117-3.1 3,214,285 10/1965 Wissinger et al 11736.4

OTHER REFERENCES IBM Technical Disclosure Bulletin, vol. 7, N0. 6, N vernber 1964, p. 421.

MURRAY KATZ, Primary Examiner. 

